Plant extracts, hydrogen peroxide

The hydride generation ICP-mass spectrometric technique [75] had a sensitivity of 6.4 ng/g selenium in plant material and was applied to digests of corn, kale and rice. In the isotope dilution mass spectrometric technique [77], the samples were spiked with 76-selenium solution and digested on a heating block at 150 °C with a mixture of nitric acid and hydrogen peroxide. Solid-phase microextraction was used to extract selenium from plant material prior to the gas chromatographic techniques [76]. See also Sects. 7.34.1 and 7.34.2. 

The aerobic oxidation of ascorbic acid by plant extracts has been attributed in the past to both traces of copper acting nonspecifically and to a specific copper-protein enzyme. The specific enzyme is now well characterized. Its action differs from that of the cupric ion-catalyzed reaction in three significant ways. Hydrogen peroxide is not formed as a product of the enzymatic reaction, while it is with cupric ions. The copper in the enzyme is about 1000 times more effective per atom as a catalyst than free copper. The enzyme exhibits a marked substrate specificity. Thus, the enzyme oxidizes L-xyloascorbic acid much more rapidly than the D-form, while cupric ions oxidize both at similar rates (D17). 

No active substance could be detected in plants treated with carboxin six weeks after the treatment. The major part of the residue found was sulfoxide. Actually, sulfoxide can occur in the plant in two ways. On the one hand, carboxin is oxidised relatively rapidly in the soil, and the plant takes up its sulfoxide, and, on the other hand, carboxin is metabolised within the plant to sulfoxide, presumably by enzyme systems producing hydrogen peroxide, such as riboflavin or flavin enzymes (Lyr et al., 1975a). It has been proved by extraction with hot dimethyl sulfate that sulfoxide formed in the plant is gradually bound in the form of a water-insoluble complex to lignin and is thus detoxified. No hydrolysis of carboxin in the plant has been observed (Chin et al., 1973). 

Leurosine, the 15, 20 a-epoxide of (285), can be prepared by oxidation of 15, 20 -anhydrovinblastine (285) with hydrogen peroxide in the presence of either horseradish peroxidase or cell-free extracts of C roseus plants the evidence has been interpreted as indicating that leurosine is also a true natural product, not an artefact. ... 

Daimler Benz, Ulm in cooperation with the Fraunhofer Institute (ICT) are setting up a process for the treatment of electronic scrap [27]. Technical University Munich operated a bench-scale SCWO-plant of 50 kg/h for the treatment of waste that could not be destroyed by biological systems. In these experiments, various model compounds were treated with hydrogen peroxide. These activities were terminated in 1996 [28]. Technical University Hambing Harbmg developed the combined process of soil extraction [29] followed by SCWO with electrolytic in-situ generation of oxygen. Soil was taken from a former paint factory, clay loam and other contaminated sites. 

The process has already been realized in a pilot plant, ft is based on oxidation with hydrogen peroxide, which is added in the aqueous phase. The formic acid added as a catalyst must be stripped after oxidation and treated. The oxidation products are then extracted from the fuel with an aluminum oxide adsorbing agent. The adsorbing agent is purified with methanol, which in turn must be regenerated for reuse. 

Polle, A., Chakrabarti, K., Schiirmann, W., and Rennenberg, H., 1990, Composition and properties of hydrogen peroxide decomposing systems in extracellular and total extracts from needles of Norway Spruce Picea abies L., Karst.), Plant Physiol. 94 312-319. 

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